This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Research performed 4 decades ago reported that a metabolic pathway where glycine was converted to oxalate, accounted for 40% of the oxalate in human urine. We recently tested the conversion of 13C-glycine to urinary oxalate in healthy subjects infused with 13C-glycine to acheive a 4% enrichment in plasma glycine. This study revealed that that the conversion of glycine to oxalate, if any, was 10%. To determine if there is a significant metabolic pathway, 6 subjects will be infused with 13C-glycine to produce a 40% enrichment of plasma 13C-glycine. In most subjects the plasma glycine level should still be within the normal range. This enrichment will enable us to determine if more than 1% of glycine is converted to oxalate. This research is important in understanding the origins of endogenous oxalate production and in identifying strategies to decrease it in individuals with oxalate-related disorders.